We propose to decrease the morbidity and mortality associated with severe aplastic anemia by continuing the evaluation of treatment by marrow grafting using HLA-identical family members as marrow donors. We hope to define the ultimate role of this approach and compare short- and long- term results to those obtained with unrelated marrow grafts and to results without marrow transplantation, Studies will address the problems of graft rejection, acute and chronic graft-versus-host disease (GVHD), infectious complications, and long-term sequelae. We will also continue exploring the usefulness of allogeneic marrow transplantation for the treatment of various genetically determined hematologic disorders including sickle cell anemia.